With the development of the Optical Transport Network (OTN), based on more and more cross scheduling applications of services of the OTN, and based on demands of total service cross capacity and scheduling flexibility, the cross scheduling is generally implemented by adopting a time slot cross mode.
When the time slot cross mode is adopted, the scheduled services are required to adopt the same clock, and frame headers should be aligned before the scheduled services are sent to a cross scheduling unit, thus each time slot in the services can be scheduled. However, if offset of the frame headers between the services to be scheduled are very large, it is required to use a cache with very large capacity before the cross scheduling unit to implement an aligning of each path of service, in which the implementation cost is much higher.
The traditional method for aligning the frame headers before each path of service is sent to the cross scheduling unit is: to provide a frame header indication signal (FP) for an access board of each path of service, which is used to serve as a sending standard of each path of service, so that the offset of the frame header of each path of service is very small before each path of service enters the cross scheduling unit and it is only needed to uses very small cache to complete the aligning of the frame header of each path of service to be scheduled. However, the method needs to provide the independent frame header indication signal for the access board of each path of service, and thus, with the increasing of services required cross scheduling, if the independent frame header indication signal is provided for all the access boards of all paths of services, lots of independent signal wires are needed which causes difficulties in design of the whole system.